He saw a familiar solidity in Glasgow.

"I think looking back at the campaign where we qualified for the Euros, our foundations were built on having a good defence," Dallas told BBC Sport NI.

While Northern Ireland won't be at the championships in Germany this time around, the victory over Denmark that concluded the otherwise disappointing qualifying campaign has now been backed up by this window's encouraging draw with Romania and victory over Scotland.

Certainly when shipping four goals to Finland last November, few would have predicted O'Neill's side would concede just once across their next 270 minutes of football and all against three sides bound for the Euros this summer too.

"You can see similarities between this team and then (2016) and this team has a lot of room to grow," said Dallas, who hopes to make his comeback from injury before the end of this season.

"Again we defended really well. We put bodies on the line, we defended really well from set-pieces.

"Michael will be over the moon with the defensive performance. They had to soak up a lot of pressure, but Bailey (Peacock-Farrell) didn't really have any saves to make bar the one at the end."

'Everyone put a shift in'

Even O'Neill's best Northern Ireland sides were ones willing to soak up pressure and hit teams on the counter or take advantage of their prowess from set-pieces.

After they enjoyed just 18% possession in the win at Hampden Park, Northern Ireland women's international Caragh Hamilton believes the next step will be to spend more time on the ball to relieve pressure on their backline.

"The defensive performance from back to front was excellent," she told BBC Sport NI.

"There are so many names that will go unnoticed for the effort they put in.

"Jamie Reid, he probably had less than 10 touches on the ball but he ran himself into the ground for 56 minutes.

"Everyone put a shift in and did their role brilliantly.

"I think going forward the thing to improve is can we maintain possession for longer? Can we rest on the ball and relieve the pressure?

"We did it a bit better in the first half than the second but when you've got those tired legs, it's difficult to stay on the ball."

Conor Bradley has been the leading light for O'Neill's young side

Optimism among the supporters will only be enhanced by the age profile of those who impressed this month too.

In addition to Dallas himself, Manchester United's Jonny Evans missed these games through injury, as did Corry Evans and Jamal Lewis, while long-serving skipper Steven Davis retired in January and joined O'Neill's backroom team for these games.

In their absence, Tuesday night's match-winner Conor Bradley has been hogging the headlines thanks to his fine displays for Liverpool this season but the likes of Shea Charles, Isaac Price and Trai Hume have all taken huge steps forward for O'Neill at international level too.

"I think he's been missing a lot of players," said Dallas.

"He didn't expect to have that backline, or even that team, when he started but he's dealt with it.

"The young lads have stepped up."